Easy Pass electronic toll cards used on the city's expressways and the M-Pass cards used on motorways heading east will each be usable on both networks from Oct 31.
The Easy Pass card, sold by the Expressway Authority of Thailand, enables motorists to automatically pay tolls on the Bangkok expressway system.
The M-Pass card, issued by the Department of Highways, is used on the Bangkok-Chon Buri-Pattaya motorway system. Motorists on this route tend to pay cash and long queues typically form at tollgates, particularly during long weekends.
Both cards require pre-payment, with the toll being deducted automatically as the vehicle passes through the gate.
Anon Luengboriroon, deputy director general of the Department of Highways, said vehicles fitted with the M-Pass card or the Easy Pass card would now be able to use the cards on the city's expressways, Motorway Route 7 (Bangkok-Chon Buri) and Route 9 (Bang Na-Bang Pa-in), media reports said.
There are 110,000 M-Pass users and 1.2 million Easy Pass card users, according to Mr Anon.
The joint use of the cards has been promised for four years. The linking of the two systems from Oct 31 will make travel easier for many motorists.